Robust Stability Analysis of a Class of LTV Systems

TL;DR

This paper develops stability conditions for a class of piecewise linear time-varying systems using LMIs, including uncertain systems, and demonstrates the approach on a space launch vehicle control problem.

Contribution

It introduces new LMI-based stability criteria for piecewise LTV systems, including robust stability conditions for uncertain cases, extending existing analysis methods.

Findings

Derived LMI conditions ensure stability of piecewise LTV systems.

Presented robust stability criteria for systems with scalar parametric uncertainty.

Validated the approach with a space launch vehicle pitch control example.

Abstract

Many physical systems are inherently time-varying in nature. When these systems are linearized around a trajectory, generally, the resulting system is Linear Time-Varying (LTV). LTV systems describe an important class of linear systems and can be thought of as a natural extension of LTI systems. However, it is well known that, unlike LTI systems, the eigenvalues of an LTV system do not determine its stability. In this paper, the stability conditions for a class of LTV systems are derived. This class is composed of piecewise LTV systems, i.e. LTV systems that are piecewise linear in time. Sufficient conditions of stability are derived in the form of linear matrix inequalities (LMIs) by using the Lyapunov stability criterion. The feasibility of LMIs guarantees the stability of a given piecewise LTV system. Furthermore, uncertain piecewise LTV systems with scalar parametric uncertainty are also considered. Sufficient conditions for robust stability of this case are also presented, which come out to be quasi-LMIs, which can be optimized using a bisection algorithm to find the bounds of uncertainty for which the system is stable. The proposed method is applied to the problem of pitch angle control of a space launch vehicle, and the results are presented.